Damping Higher Frequency Resonance of Grid Connected DFIG System

A grid-connected DFIG system may suffer from High-Frequency Resonance (HFR) under a shunt compensated weak grid network. The net negative resistance of the entire system and the inappropriate phase response difference between the DFIG system and the shunt compensated weak network at the frequency magnitude intersection points are the direct cause of the resonance instability in the system. This study discussed the details of HFR analysis based on the complete impedance model of the grid-connected DFIG system. An HFR damping strategy based on virtual impedance was proposed and demonstrated to introduce positive resistance and phase lead compensation to prevent HFR instability. Finally, time-domain simulations were performed to validate the theoretical HFR analysis as well as the proposed damping strategy.